Increased survival by feeding tetradecylthioacetic acid during a natural outbreak of heart and skeletal muscle inflammation in S0 Atlantic salmon, Salmo salar L.

We have previously documented increased survival by feeding tetradecylthioacetic acid (TTA) during a natural outbreak of infectious pancreatic necrosis in post-smolt S1 Atlantic salmon. The aim of the present study was to test the effects of dietary TTA in S0 smolt at a location where fish often experience natural outbreaks of heart and skeletal muscle inflammation (HSMI) during their first spring at sea. The experimental groups were fed a diet supplemented with 0.25% TTA for a 6-week period prior to a natural outbreak of HSMI in May 2007. Relative percent survival for the groups fed TTA was 45% compared with control diets, reducing mortality from 4.7% to 2.5%. Expression of genes related to lipid oxidation was higher in cardiac ventricles from salmon fed TTA compared with controls. In addition, salmon fed TTA had periodically reduced levels of plasma urea, and increased cardiosomatic index and growth. Reduced mortality and increased growth after administration of TTA may be related to a combination of anti-inflammatory effects, and an altered metabolic balance with better protein conservation because of increased lipid degradation.     

Reduction of early sexual maturation in male S0 Atlantic salmon (Salmo salar L.) by dietary supplementation of tetradecylthioacetic acid (TTA)

Effects of dietary tetradecylthioacetic fatty acid (TTA) on muscle fat, development of gonads and early sexual maturation in S0 Atlantic salmon during the first year in sea were investigated. TTA (0.5% w/w) was added to the feeds for 8 weeks in the spring. In May, at the end of the TTA‐feeding period, the fish in the TTA group had significantly (P < 0.05) less fat (10.1%) stored in muscle compared with the control group (10.8%). In September, mean male gonadosomatic index (GSI) in maturing fish in the TTA group was found to be lower compared with the maturing fish in the control group (P = 0.05). On the basis of GSI values, male sexual maturation in September was 10.0% vs. 14.4% for the TTA and the control group respectively. Thus, relative to the control group, the incidence of male sexual maturation in the TTA group was reduced by about 1/3 (P = 0.002). Production data was not affected by dietary supplementation of TTA. This study reveals that TTA significantly reduces the incidence of male sexual maturation in S0 Atlantic salmon. A significant elimination model of TTA in fish muscle that takes into account, the growth rate of the fish was further developed in this study.     

The minimum dietary requirement of vitamin C in Atlantic salmon (Salmo salar) fry using Ca ascorbate-2-monophosphate as dietary source

The minimum dietary vitamin C requirement for optimal growth and normal development in Atlantic salmon (Salmo salar) fry at the onset of feeding was studied, using Ca ascorbate-2-monophosphate (AP) as dietary source. The requirement was established by means of a feeding study lasting for 23 weeks from the beginning of feeding. The practical diets used were supplemented with AP at levels of 0, 10, 20, 40, 80 and 160 mg ascorbic acid (AA) equivalents/kg. Growth, mortality, hydroxyproline content in skin and backbone, and AA in liver were recorded to evaluate the results. The results suggest that the minimum dietary requirement for optimal growth and normal development is in the range of 10–20 mg AA equivalents/kg dry diet during the period studied.     

Does the capacity for energy utilization affect the survival of post‐smolt Atlantic salmon,Salmo salar L., during natural outbreaks of infectious pancreatic necrosis?

If osmotic stress and reduced seawater tolerance are predisposing factors for infectious pancreatic necrosis (IPN) outbreaks in farmed Atlantic salmon, increased survival by enhancing access to energy would be expected. The aim of the present study was, therefore, to increase energy access in 1-year old Atlantic salmon after sea transfer by increasing the level of dietary fat, by exchanging some of the dietary oil with more easily oxidized medium chain triacylglycerols, or by dietary supplementation of potentially energy enhancing additives such as clofibrate and tetradecylthioacetic acid (TTA). A natural outbreak of IPN occurred 8 weeks after sea transfer, and a significant dietary effect explaining 76% of the variation in mortality was observed. Relative percentage survival for the fish fed TTA in sea water was 70% when compared with the unsupplemented control, reducing mortality from 7.8 to 2.3%. Muscle fat content and plasma chloride were related to IPN mortality, suggesting that reduced hypoosmoregulatory capacity might be a predisposing factor to the onset of an IPN outbreak. Based on the observation of a threefold increase in white muscle mitochondrial fatty acid oxidizing activity by TTA, it is suggested that TTA has resulted in a re-allocation of dietary fatty acids from storage to energy producing oxidation.     

Evaluation of an alkane yeast (Candida sp.) as a substitute for fish meal in Oregon Moist Pellet: Feeding trials with coho salmon (Oncorhynchus kisutch) and rainbow trout (Salmo gairdneri)

Up to 40% of the fish meal portion of the Oregon Moist Pellet (OMP) was replaced with up to 40% alkane yeast single cell protein (22% of dietary protein) in diets fed to rainbow trout in fresh water, and up to 100% of the fish meal portion was replaced with alkane yeast (54% of dietary protein) in OMP diets fed to coho salmon in salt water. Salmon diets were supplemented with DL-methionine to correct for a suspected deficiency in this essential amino acid. Alkane yeast was an acceptable substitute for fish meal at all levels tested in trout. Only 25% yeast substitution was judged to be acceptable in the OMP diet for marine-cultured coho salmon, causing less than 4% reduction in growth. In marine-cultured coho salmon, growth was depressed further at fish meal substitution levels greater than 25%, while supplementation with DL-methionine enhanced growth and feed conversion only slightly.     

Supplementation of various meals to fish meal diet for chum salmon fry

In a 6-week feeding experiment, chum salmon, Oncorhynchus keta, swim-up fry, were fed fish meal diets supplemented with silkworm pupae powder (5%), dried beef liver (5%), krill meal (5%) or earthworm powder (5%) at the expense of fish meal, or substituting glucose (13%) for dextrin. Fish fed the diet with earthworm powder showed the best growth performance (675% weight gain in 6 weeks) and feed efficiency (117%). The growth rate and feed efficiency of the krill meal group were also significantly better than those of the control group (without supplement or substitution). Substitution of glucose and supplementation of silkworm pupae or beef liver failed to improve the growth rate, but significantly improved feed efficiency. Food consumption of fish fed the diet supplemented with earthworms was lowest, and none of the dietary treatments appreciably increased food intake of the fish over that of the control group. The dietary group receiving earthworm powder also showed significantly higher body fat content than the remaining dietary groups. No significant differences were noted in body protein and ash contents among all dietary treatments.     

The influence of environmental temperature on the apparent nutrient and fatty acid digestibility in Atlantic salmon (Salmo salar L.) fed finishing diets containing different blends of fish oil, rapeseed oil and palm oil

A 12‐week feeding trial was conducted to investigate the interactive effects between water temperature and diets supplemented with different blends of fish oil, rapeseed oil and crude palm oil (CPO) on the apparent nutrient and fatty acid digestibility in Atlantic salmon. Two isolipidic extruded diets with added fish oil fixed at 50% and CPO supplemented at 10% or 25% of total added oil, at the expense of rapeseed oil, were formulated and fed to groups of Atlantic salmon (about 3.4 kg) maintained in floating cages. There were no significant effects (P>0.05) of diet on growth, feed utilization efficiency, muscle total lipid or pigment concentrations. Fatty acid compositions of muscle and liver lipids were mostly not significantly different in salmon fed the two experimental diets but showed elevated concentrations of 18:1n‐9 and 18:2n‐6 compared with initial values. Decreasing water temperatures (11–6°C) did not significantly affect protein, lipid or energy apparent digestibilities of the diets with different oil blends. However, dry matter digestibility decreased significantly in fish fed the diet with CPO at 25% of added oil. Increasing dietary CPO levels and decreasing water temperature significantly reduced the apparent digestibility (AD) of saturated fatty acids. The AD of the saturates decreased with increasing chain length within each temperature regimen irrespective of CPO level fed to the fish. The AD of monoenes and polyunsaturated fatty acids was not affected by dietary CPO levels or water temperature. No significant interaction between diet and water temperature effects was detected on the AD of all nutrients and fatty acids. The results of this study showed that the inclusion of CPO up to about 10% (wt/wt) in Atlantic salmon feeds resulted in negligible differences in nutrient and fatty acid digestibility that did not affect growth performance of fish at the range of water temperatures generally encountered in the grow‐out phase.     

Effect of dietary taurine supplementation on growth performance of yellowtail juveniles <Emphasis Type="Italic">Seriola quinqueradiata</Emphasis>

ABSTRACT:   The effect of taurine on growth of yellowtail juveniles Seriola quinqueradiata was investigated by a feeding experiment of diets containing various taurine levels. Test diets supplemented with 0, 0.5, 1.0, 1.5 and 2.0% of taurine were prepared. These diets were fed to yellowtail juveniles with an initial mean body weight of 0.5 g for 6 weeks. Supplementation of taurine in the diet of yellowtail improved their growth performance significantly ( P  < 0.05) over the initial 3-week period. The fish fed with the taurine-supplemented diet improved in percent gain and feed efficiency over both 3 and 6 weeks. Taurine content in the muscle proportionally increased with the dietary taurine level. The fish fed without supplemented taurine diet showed higher contents of serine in the muscle. With each increase in the inclusion level of taurine content in the diet, the concentration of serine in the muscle decreased. The cystathionine content in the muscle of each group was unchanged. These results suggest that taurine supplementation in the diet not only improves growth but also affects the sulfur amino acid metabolism of yellowtail juveniles.     

Dorsal aorta cannulation: a method to monitor changes in blood levels of astaxanthin in voluntarily feeding Atlantic salmon, Salmo salar L.

This study was undertaken to assess dorsal aorta cannulation as a method to evaluate alterations in diet composition and feeding protocol on pigment retention in salmonid fish. Temporal changes in blood astaxanthin concentrations of dorsal aortacannulated Atlantic salmon, Salmo salar L., were followed in relation to variations in dietary pigment concentration and fish-feeding husbandry protocol. The fish were held individually in 200-L fibreglass tanks supplied with running sea water. Each fish was forced to swim at 0.5 body lengths s^?1 and was fed daily by hand to satiation. The fish had an average growth rate of 1% day^?1. Blood astaxanthin concentrations were noted to be highly correlated (r= 0.995) with dietary levels of astaxanthin, but not as well correlated (r= 0.71) with total gut content of this pigment. Marked variations in blood astaxanthin concentration were noted between individual fish at each dietary pigment concentration, but the ranking of the fish was generally unaffected between each dietary pigment level. After cessation of feeding a diet supplemented with 75 mg of astaxanthin kg^?1, salmon fed a diet with no pigment showed more-rapid blood pigment clearance than those that were starved. Likely, feed remaining in the alimentary tract of the starved fish functioned as a reservoir of pigment for the blood until the intestinal tract was empty. Blood pigment levels were not depressed in salmon fed a diet supplemented with 75 mg of astaxanthin kg^?1 once daily instead of twice daily.     

Effect of taurine supplementation on the metabolism and body lipid‐to‐protein ratio in juvenile Atlantic salmon (Salmo salar)

Previously, we reported that methionine intake determined the taurine concentration in the liver of on‐growing Atlantic salmon fed plant protein diets. Further, the methionine intake and/or the increased taurine concentration following increased methionine intake affected the liver lipid metabolism. The following study therefore aimed to test whether taurine affected the growth or the type of growth when added in high plant protein diets naturally low in taurine but equal and adequate in dietary methionine. Juvenile Atlantic salmon [initial body weight (BW) of 2 g] were fed plant protein diets (16.5% fishmeal), which were supplemented with taurine or not for a period of 56 days. As a control for growth and normal metabolism, a fishmeal‐based commercial diet (68% fishmeal) was used. Supplementation with taurine to high plant protein diets had a slightly negative effect on weight gain, but the final body weight was not different. Interestingly, the pool of free amino acids in the liver and muscle was significantly higher in fish fed the supplemented diet as compared with fish fed the plant protein diet without taurine supplementation. Liver polyamine concentration was higher in fish fed the supplemented diet than in fish fed the similar diet without supplementation. Additionally, juvenile salmon fed the plant‐based diet supplemented with taurine had a lower body lipid‐to‐protein ratio due to a reduced whole‐body lipid content, while the whole‐body protein content was similar between treatments. Our study thus indicates that the addition of a low concentration of taurine to high plant protein diets interacts with lipid metabolism and storage, concomitantly affecting the general metabolism as the concentrations of the free amino acids and polyamines in the liver were significantly higher. The possible reasons for these changes are discussed.     

Long-term effects of dietary fat level and feeding rate on growth, feed utilization and carcass quality of Atlantic salmon

Two extruded diets designed to have fat levels of 220 g kg⁻¹ (F22) and 300 g kg⁻¹ (F30) were fed to Atlantic salmon Salmo salar L. in two different experiments during the sea rearing period (from 0.2–0.3 kg to 3–4 kg). Each diet was fed restricted and isoenergetically at two feeding rates to fish in triplicate groups. In one of the experiments, a supplementary group of fish was fed to satiation with the F30 diet. All fish were slaughtered and evaluated for quality according to a commercial standard.
No difference in growth was observed between fish fed the two diets at similar feeding rates and the growth was proportional to the amount of dietary energy offered. Feed conversion ratios decreased according to higher energy content in the F30 diet, and the nitrogen and phosphorus retention increased significantly. Fish fed the F30 diet revealed a higher incidence of sexual maturity. Fat content in cutlets and dressed carcasses were significantly affected by feeding rate but not by dietary fat level. Fish fed the F30 diet had more visceral fat and, consequently, lower dress-out percentage. Mortality, liver size and liver colour were not significantly affected by dietary fat level.
These experiments showed that even large differences in dietary fat level employed for the entire sea rearing period of Atlantic salmon, did not, or only marginally affected the cutlet and dressed carcass fat content. The high fat diet improved the feed utilization, thus decreasing the discharge to the environments. Furthermore, it resulted in greater growth at ad libitum feeding.     

Supplementing copper to a fish meal based diet fed to Atlantic salmon parr affects liver copper and selenium concentrations

The present experiment was conducted to study growth and tissue responses in Atlantic salmon, Salmo salar L., fed a fish meal based diet supplemented with copper (Cu). The findings of the experiment were used to evaluate the need for dietary Cu supplementation. Atlantic salmon parr, initially weighing ≊ 7.5 g, were randomly distributed among 10 tanks, with 300 fish in each tank. Duplicate groups of fish were fed a fish meal based diet containing 3.5 mg Cu kg⁻¹, or this diet supplemented with 5, 10, 50 or 100 mg Cu kg⁻¹ (as CuSO₄*5 H₂O) for 12 weeks. Growth was recorded and blood haemoglobin measured. The Cu concentrations in whole body, liver, serum and selected muscle samples were measured, as was liver selenium (Se) concentration.
There were no difference in growth among the dietary treatments. There were, however, significant differences among the dietary groups in liver Cu and Se concentrations. The fish fed the diet supplemented with 5 mg Cu kg⁻¹ had increased liver Cu concentration compared with the other groups. Similar trends were found for serum Cu concentration and whole-body Cu concentration, but these effects were not significant. Liver Cu and Se concentrations were positively correlated and liver Se concentrations were inversely correlated to dietary Cu concentration, confirming an interaction between these two elements in salmon.
There may be a positive effect of a modest Cu supplementation level, and we suggest that a small amount of Cu (5–10 mg kg⁻¹) should be added to fish meal based diets.     

Effect of dietary protein reduction with synthetic amino acids supplementation on growth performance,digestibility, and body composition of juvenile Pacific white shrimp, <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis>

Two experiments were conducted to evaluate the effect of lowering crude protein level and fish-meal inclusion rate by using commercially available synthetic amino acid supplements in practical diets on the growth performance of Litopenaeus vannamei. In experiment 1, three diets were formulated to assess whether 50% of fish meal could be replaced by soybean meal with synthetic amino acid supplementation. Diet 1 was formulated as the normal control with 20% fish meal and 36% crude protein; diet 2 was the negative control with 34% crude protein and half of the fish meal was replaced with soybean meal; and diet 3 was similar to diet 2 but was supplemented with amino acids to ensure the level of lysine, methionine plus cystine, and threonine similar to that in the diet 1. After a 70-day feeding trial, weight gain and specific growth rate of shrimps fed diet 2 were significantly lower than those fed diet 3, and numerically lower than those fed diet 1. Feed intake of shrimps fed diet 3 was significantly higher than those fed diets 1 and 2. There were no significant differences in feed conversion ratio among shrimps fed different diets. In experiment 2, four diets were prepared with diet 1 as the normal control with 41.26% crude protein, diets 2–4 were formulated to contain 39.81, 38.40, and 35.52% of crude protein with synthetic amino acids were added to simulate the amino acid levels of the diet 1. After a 70-day feeding trial, it was found that reducing dietary crude protein from 41.26 to 35.52% did not affect weight gain or feed conversion ratio. The survival of crude protein 35.52% treatment was significantly lower than other treatments. No difference was observed in body protein, lipid composition, and apparent digestibility coefficient among dietary treatments. Results of this study suggested that dietary crude protein could be reduced from 41.26 to 35.52% in the diets of L. vannamei as long as synthetic amino acids were supplemented.     

Effects of dietary canola oil level on growth, fatty acid composition and osmoregulatory ability of juvenile fall chinook salmon (Oncorhynchus tshawytscha)

This study assessed refined canola oil (CO) as a supplemental dietary lipid source for juvenile fall chinook salmon, Oncorhynchus tshawytscha, parr with respect to possible effects on their growth and osmoregulatory performance and body composition. Diets with equal protein ( 57%) and lipid ( 19%) content (dry weight basis) were supplemented with lipid from either anchovy oil (AO) or CO with AO so that CO comprised 0 (0CO), 11% (11CO), 22% (22CO), 33% (33CO), 43% (43CO) or 54% (54CO) of the dietary lipid content. Triplicate groups of juvenile chinook salmon were fed their prescribed diets for 104 days in freshwater (FW) and 31 days in seawater (SW) after a 4-day transition period. Dietary fatty acid compositions reflected the different proportions of AO and CO in the supplemental lipid. Diet treatment had no effect on fish growth, feed intake, feed efficiency, protein utilization, fish mortality or terminal whole body water and ash percentages. Whole body lipid percentages were higher in 11CO and 43CO fish than in 33CO fish and in 11CO fish versus 22CO fish. Whole body protein percentages were highest in 33CO, 43CO and 54CO fish and lowest in 0CO and 22CO fish. Terminal whole body fatty acid compositions were influenced strongly by the dietary fatty acid compositions. Haematocrit and muscle water percentages were not affected consistently and plasma Na⁺ and Cl⁻ concentrations were unaffected by diet treatment in FW or 24-h seawater challenges during FW residency. Also, diet treatment had no effect on the physiological parameters after SW residency. We conclude that dietary treatment had no effect on fish growth performance under our experimental conditions. Also, the dietary inclusion of CO neither facilitated nor impaired the transfer of chinook salmon parr to seawater. Thus, CO was found to be an excellent and cost-effective source of supplemental dietary lipid for culture of juvenile fall chinook salmon during freshwater residency.     

Effects of Feeding High Monounsaturated Sunflower Oil Diets on Sensory Attributes of Salmonid Fillets

The purpose of this study was to determine if substituting high oleic acid sunflower oil for herring oil in formulated salmonid diets affected sensory attributes of fillets from coho salmon (Oncorhynchus kisutch) and rainbow trout (Oncorhynchus mykiss). Two feeding trials were conducted in which coho salmon and rainbow trout were fed diets containing either high oleic acid sunflower oil or herring oil as the supplemental lipid source (12.4% of the diet by weight) for 6-8 weeks. In standard directional triangle tests on previously frozen rainbow trout and coho salmon fillets stored at 5¦C for up to 10 days, a significant number of panelists were able to differentiate between fillets from the two dietary treatments based on aroma, and determined that the herring oil fillets had a ôfishierö aroma than the sunflower oil fillets. The panelists tended to prefer rainbow trout fillets from the sunflower oil treatment to fillets from the herring oil dietary treatment. These results suggest that increasing the monounsaturated fatty acid level in fish by feeding a high monounsaturated fatty acid finishing diet could potentially decrease oxidative rancidity, a major cause of quality deterioration in aquatic food products, and thereby improve the shelf life and sensory characteristics of the fillets.     

Bioavailability and interactions with other micronutrients of three dietary iron sources in Atlantic salmon, Salmo salar, smolts

Atlantic salmon, Salmo salar L., with mean initial weight of 60 g were fed a diet based on cod muscle meal supplemented with elemental iron, iron sulphate or haem-bound iron in concentrations of 0, 25, 50, 100, 500 and 1500 mg iron kg^?1 for 8 weeks. No significant differences in growth or mortality were found, except in fish fed 1500 mg haem iron kg^?1, which showed reduced growth. In fish fed diets supplemented with elemental iron below 1500 mg iron kg^?1, blood haemoglobin and hepatic iron concentration decreased compared with fish fed the unsupplemented diet. Fish fed diets supplemented with iron sulphate showed increased blood haemoglobin and hepatic iron concentrations between 25 and 100 mg iron kg^?1. Fish fed diets supplemented with haem-bound iron showed increased hepatic iron at all dietary iron levels, while blood haemoglobin concentration decreased in the group fed 1500 mg haem iron kg^?1. The bioavailability of haem iron relative to sulphate iron was calculated by the slope ratio method to be 239% and 148% using blood haemoglobin and hepatic iron, respectively. Relative bioavailability of elemental iron was zero when dietary supplementation levels were between 25 and 500 mg iron kg^?1, while a small part was utilized when 1500 mg elemental iron kg^?1 was supplemented. Additions of 500 and 1500 mg haem-bound iron kg^?1 resulted in a complete loss of ascorbic acid in these diets. When these groups were discounted, no significant relationship between hepatic iron and hepatic ascorbic acid was found. There was no significant effect of dietary iron on whole-body manganese concentration and only a weak effect on whole-body zinc concentration. No significant correlations between dietary iron and hepatic copper concentration were found in any of the dietary treatments. This study also showed that the level of inorganic iron supplementation may be reduced by inclusion of 20 g blood meal kg^?1 in the diet.     

Effect of dietary ω3 and ω6 fatty acids on growth and feed conversion efficiency of coho salmon (Oncorhynchus kisutch)

Sixteen isocaloric diets varying only in the levels of ω3 and ω6 fatty acids were prepared. Each diet was fed to duplicate groups of coho salmon for 14 weeks. At termination, the final weight of each diet group fish was determined. The optimum level of dietary ω3 fatty acid ranged from 1% to 2.5%. Dietary ω6 fatty acid higher than 1% depressed fish growth. Fish growth, feed conversion efficiency, fish mortality and fatty acid composition of fish phospholipids were determined.     

Effects of dietary arachidonic acid on final maturation,spawning and composition of gonad of black sea urchin Diadema setosum (Leske, 1778)

This study investigated the effect of dietary arachidonic acid (ARA, 20:4n‐6) on final maturation, spawning performance and composition of the gonad of black sea urchin (Diadema setosum). Four different dietary ARA levels of 0.3 g/kg (Control diet), 1.4 g/kg (ARA 1.4), 2.5 g/kg (ARA 2.5) and 3.7 g/kg (ARA 3.7) were prepared and tested in this feeding trial for 90 days. The result showed that growth in terms of weight was not relatively affected by dietary ARA. Gonadosomatic Index (GSI) of animals were gradually increased in all the diets throughout the trial. The highest GSI level (25.7 ± 3.16%) was observed in animals fed with the diet ARA 1.4. ARA content in the gonad proportionally increased with dietary ARA levels. The highest larval survival rate (85.5 ± 5.67%) was found in diet ARA 2.5. The results of this study indicate that ARA plays an important role in the reproduction functions of black sea urchin and supplementing an appropriate level of ARA in the broodstock diet could induce the final maturation and improve reproduction of black sea urchin, but a higher level of ARA (3.7 g/kg) seems to have a negative effect on both growth rate and GSI.     

The effect of dietary chitin on growth and nutrient digestibility in farmed Atlantic cod,Atlantic salmon and Atlantic halibut

The effect of adding 0%, 1%, 2% and 5% chitin from prawn shells in the diets for Atlantic cod, Atlantic halibut and Atlantic salmon on growth was investigated. Nutrient digestibility and feed utilization was investigated in salmon and cod. Atlantic cod grew from 186 ± 29 to 383 ± 78 g (N = 960) over 13 weeks. Dietary chitin had no effect on length, weight, condition, liver size or specific growth rate (SGR). The apparent digestibility (ADC) for protein ranged from 84.7% to 86.5%, lipid between 88.8% and 93.1% and dry matter from 96.1% to 96.6%. Feed utilization varied between 1.08 and 1.11 and was not correlated with dietary chitin content. Atlantic salmon tripled their weight from 199 ± 9 to 615 ± 75 g (N = 480) during the 13 weeks. High inclusions of chitin (>1%) reduced both growth rate and condition. Protein and lipid ADC was negatively correlated with dietary chitin. Feed utilization ranged between 0.86 and 0.90 and was not significantly affected by dietary chitin. Faecal protein increased significantly with increasing dietary chitin, while faecal dry matter and lipid did not. Individually tagged Atlantic halibut grew from 1300 ± 470 to 2061 ± 714 g (N = 70) during 6 months. Individual growth rates varied within each group from being slightly negative to 0.81%·day^?1. Diet had no significant effect on growth rates. Atlantic cod and Atlantic halibut seems unaffected by up to 5% chitin additions in the diet, while chitin >1% of diet negatively affects growth and nutrient utilization in Atlantic salmon.     

Influence of terrestrial lipid and protein sources and activated carbon‐treated fish oil on levels of persistent organic pollutants and fatty acids in the flesh of Atlantic salmon

Reductions in flesh contaminant concentrations were evaluated in a 36‐week feeding trial examining several dietary techniques. Atlantic salmon were fed one of seven dietary treatments for 24 weeks. These diets included a fishmeal, fish oil control diet, an industry control diet, three diets that examined a 75% replacement level of anchovy oil (AO) with flaxseed oil, canola oil and poultry fat, and two diets formulated to be low in contaminants formulated with canola oil, activated carbon‐treated anchovy oil and canola protein concentrate or soy protein concentrate. Following this initial 24‐week feeding interval, a 12‐week finishing diet was utilized to restore the levels of omega‐3 highly unsaturated fatty acids (n‐3 HUFAs). The salmon had marked reductions in their flesh concentrations of total polychlorinated biphenyls (PCBs), dioxin‐like PCBs and total toxic equivalents by the end of the grow‐out phase, but also exhibited significant depressions in their flesh concentrations of n‐3 HUFAs relative to 100AO‐fed fish. The 12‐week finishing diet period was effective in partially re‐instating omega‐3 levels to those present in the flesh lipids of fish fed 100AO while concurrently maintaining lower flesh contaminant concentrations.